Militarism

Military was one main cause of World War 1. As technology and countries became more advanced, countries engaged in arms race. Countries increased their militaries by amassing weapons, troops/soldiers, and they also improved their navies.

Alliances

Alliances were some of the most difficult things. Example: Austria-Hungary went to war with Serbia, Russia got involved defending Serbia. Germany then declared war on Russia; meanwhile France was drawn against Germany and Austria-Hungary. Germany attacks France through Belgian bringing Britain into this mess of a world. Just then Japan is here, then later Italy and the U.S. come in. See, it's a really big mess.

Nationalism

Every country was proud of its own. In this, other countries thought they could take control of others, this caused a lot of fighting.

Imperialism

Imperialism is a nation’s conquest of other territories around the world. So you can see how this would cause conflict. Ex: I take control you you, you fight back, and all MANIA breaks lose.

Assasination of Archduke Ferdinand

The assassination of this man was difficult. Austria-Hungary's control over Serbia and regions of Europe were ceased because of this, too.